chore: update actions/deploy-pages to latest

Author: ojeytonwilliams

.github/workflows/mdbook.yml

@@ -54,4 +54,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@de14547edc9944350dc0481aa5b7afb08e75f254 # v2
+        uses: actions/deploy-pages@v4 # v2